resizeable arrays: T[new]

[Bill Baxter]

Tom S wrote:
> Derek Parnell wrote:
>> On Mon, 04 Jun 2007 10:45:09 -0700, Walter Bright wrote:
>>
>>>>>    T[n]   a;  // static array
>>>>>    T[]    b;  // dynamic array
>>>>>    T[new] c;  // resizeable array
>>>> I'd propose a different nomenclature:
>>>>
>>>> T[n]   a;  // static array
>>>> T[]    b;  // (array) slice
>>>> T[new] c;  // dynamic array
>>> I like "resizeable" array because it is pretty clear what it does.
>>
>> I think you are quite wrong Walter. The new interpretation of 'x[]' is
>> almost identical to what we used to think of as a slice. And the
>> interpreatation of 'x[new]' is exactly what used to be known as a dynamic
>> array.
>> Your change will effect all code immediately whereas reversing the
>> (changed) meaning of '[]' and '[new]' to mean 'resizable' and 'slice' 
>> will
>> allow coders to change their coding over time. Unless of course that's 
>> what
>> you are trying to do ...
> 
> Except that the non-resizable arrays will be more common in use than the 
> fully dynamic ones. Thus, the resizable are a special case and deserve 
> special syntax. *Except* that it's similar to const-by default, while D 
> will use mutable-by default.

I think it really depends.  I can imagine for a lot of folks it will 
basically boil down to parameter vs. local variable.  If it's a 
parameter you want slice-semantics, if it's a local variable you want 
resizeable semantics.  A quick grep through my code gave me about 400 
lines where I used '~='.  That doesn't tell you all that much, but it 
does give something close to an upper bound.  For each of those lines a 
T[] somewhere is going to need to be changed to a T[new] (or whatever). 
The number could be less if I'm using auto.  But I also use
    T[] x; x.length = N;
a lot.  Those will need to be changed too.

On the other hand "[]" appears about 1700 times.  That says to me that 
arrays that I don't resize (whether in paramter or not) are probably 
significantly more common than those I do.  But either way it's a 
significant amount of code to change.

--bb